1. Field of the Invention
The present invention relates generally to a communication electronic device and an antenna structure thereof, and more particularly, to a communication electronic device having a small-size planar antenna utilizing parallel resonance to generate multi-band operation.
2. Description of the Prior Art
With the rapid development of mobile communication technologies and markets, wireless access capabilities are indispensable to portable communication electronic devices. In addition to wireless local area network (WLAN), wireless wide area network (WWAN) is able to provide services over a wide coverage, and long term evolution (LTE) technology can provide higher data rates, thereby improving convenience and providing real time in wireless access while using the portable communication electronic devices. On the other hand, slim-profile design is becoming more attractive in market for the communication electronic device. Hence, it is critical to design a planar printed antenna having the capability of covering multi-band operation for a slim mobile device.
U.S. Patent (U.S. Pat. No. 7978141 B2) entitled “Coupled-fed multi-band loop antenna” discloses designing a dual-band antenna used in a communication electronic device, wherein the antenna has two operating bands. However, the lower operating band of the antenna fails to cover multi-band operation. As a result, such an antenna cannot be applied for covering all the lower operating bands in the WWAN or LTE system.
Apparently, it is necessary to provide a communication electronic device, which has two wide operating bands. For example, the operating bands can cover 824˜960 MHz as well as 1710˜2170 MHz. Additionally, the antenna element should have the attractive characteristics of planar structure and small size.